1. Field Of The Invention
The present invention relates to a novel cell harvester providing for the rapid separation of solids from a carrier fluid without contamination in biochemical testing and screening. More particularly, the invention pertains to a method and apparatus for the rapid and simultaneous separation of chemical components such as for example the separation of bound ligand receptor complexes from the free ligand without contamination from a group of ordinary laboratory test tubes. The cell harvester is capable of simultaneously filtering a number of samples onto defined areas of a single sheet of filter medium without risk of contamination from outside sources or infiltration from one sample to another.
2. Description of the Prior Art
The measurement of various body constituents by the use of radio receptors and radioimmunoassays has in recent years achieved widespread acceptance. Some of the research in diagnostic uses include drug screening, basic research into receptor functions, measurement of aldosterone, angiotensin, hepatitus B antigen, insulin, thyroid stimulating hormone and vitamin B 12.
Radioimmunoassay procedures require a suitable separation technique in order to recover the bound component from the free labeled tracer material. The procedures used for separation have varied widely and have included developments in electrophoresis, chromatography, ion exchange, absorption to dextran coated charcoal, talc or cellulose and a number of solid phase antibody separation techniques.
A few of the widely accepted and utilized practices of solid phase separation for a radioimmunoassay include the covalent bonding of an antibody to an insoluble polymeric material and the physical adsorption of an antibody onto an insoluble polymeric substrate. The resulting product of such separation procedures is a residue of solid matter which may be subjected to further reactions or further analysis such as microscopy, radioisotope detection or spectrophotometry.
Solid phase antibody separation techniques have the distinct advantage of ease and convenience by allowing the separation and isolation of the bound ligand from the free labeled tracer material by a simple washing procedure at the completion of the immune reaction. In practice however this washing stage of the prior art has required several time consuming and repetitive steps by the laboratory technician due to the often large number of samples which must be sequentially tested and analyzed. These traditional washing techniques create a significant risk of contamination thereby increasing the cost and impeding and compromising the progress of the research.
In general, analytical and quantitative testing of particulate biochemical substances are carried out in ordinary laboratory test tubes, vials or other commercially available containers which are collected in an array. Many of the prior art techniques of separation of the desirable constituents utilizes filter arrangements which require the technician to pour or otherwise individually transfer a large collection of samples from the test tubes to the various wells of a specially designed filtering apparatus. Examples of such prior art filtering devices and procedures are disclosed in Cleveland U.S. Pat. Nos. 4,427,415 and Fernwood 4,493,815.
U.S. Pat. Nos. 4,427,415 and 4,493,815 pertain to vacuum assisted filter systems for the simultaneous separation of a number of biochemical samples. These devices in some cases employ a single sheet of a filter medium clamped between a pair of plates having a plurality of cooperating apertures or passages identifying a collection area on the filter. The upper plate is provided with a plurality of sample wells to form a grid like structure. In operation the individual samples are sequentially introduced into each of the wells from the test tubes and a vacuum is applied to the lower face of the bottom plate to draw the carrier fluid through the device thereby depositing the desired residue on the filter element. This arrangement requires tedious and time consuming procedures to transfer each of the many samples individually to the sample wells of the filter device thereby increasing the risk of incorrectly labeling the filtered samples and contamination from outside sources as well as encroachment of samples from one collection area on the filter to another.
Another form of the prior art filtering devices is disclosed in Chen U.S. Pat. Nos. 4,090,850 and Leder 3,319,792 pertaining to the use of individual filtering elements such as an antibody coated cellulose placed into a plurality of separable wells cooperating with a receiving structure. After the samples are manually added individually to each of the wells a vacuum is applied to the receiving structure to draw the sample through the filter. This prior art arrangement also suffers from the distinct disadvantage of requiring tedious and time consuming procedures in positioning individual filter papers in each of the numerous wells and transferring each sample to the sample well in a singular fashion thereby increasing the risk of contamination of the samples.
A further type of device is disclosed in Hein U.S. Pat. No. 4,415,449 relating to a bench supporting a number of conventional filter flasks and filter devices. This arrangement is generally not suitable for biochemical filtering and particularly radio-immunoassay testing procedures due to the risk of contamination and time consuming operation.
Another form of prior art biochemical filtering device is disclosed in Meakin, U.S. Pat. No. 4,167,875, where a filter housing is defined by a sample well, a filter manifold and a cutting block. The cutting block is provided with projections such that when clamped to the filter manifold a single sheet of filter medium is cut into circular shaped elements corresponding to the filtering wells. A conduit extends from the filter housing to the sample tray such that when a vacuum is applied to the filter housing the sample fluid is drawn upward through the conduit and through the filter element. This arrangement is relatively complex and elaborate in providing conduits to draw the sample from the wells to the filter and the means for feeding, positioning and cutting the filter medium. The speed and number of samples which can be filtered at one time are limited since in order to proceed to the next set of samples it is necessary to reposition the assembly, remove the filter elements and feed new filter material to the filter assembly. Moreover, the arrangement does not provide a closed filtering assembly which will ensure accurate and uncontaminated results.
A further example of the prior art filtering devices is disclosed in Weinstein U.S. Pat. No. 4,245,042. This device pertains to harvesting cells from a plurality of wells of a standard culture plate utilizing an upper block housing a vacuum conduit and a lower block housing a washing fluid conduit. The upper and lower blocks are adapted to be attached together thereby sandwiching a filter element in between. A number of tubes are provided extending downwardly from both the vacuum and wash conduits which are to be inserted into the sample wells. In operation a sample fluid is drawn from the wells by a vacuum upwardly through the filter element. The numerous conduits and tubes required to draw the sample from the culture plate and the necessity of carefully assembling the unit to insure proper positioning of the tubes in the wells to avoid contamination of the samples result in an arrangement which is fairly complex to effectively operate and expensive to produce.
All of the above described filtering devices require time consuming operations in preparing and setting up the filter operation. Additionally some of the devices require extensive manual transfer of the various samples to the wells of the filter arrangement thereby increasing the time required for effective testing and creating a greater risk of error and contamination of the samples. The prior art devices that have sought to reduce the amount of manual labor and handling of samples have resulted in complex and relatively expensive components which have not guaranteed consistent and accurate results for application to state of the art radioimmunoassay and biochemical separation requirements. The demands of modern radioimmunoassay and biochemical separations and isolation procedures have developed a requirement for a filtering device which is inexpensive and easy to operate and is able to provide rapid testing and simultaneous separation of a large number of samples while maintaining accuracy and achieving reliable results. There is further a need for a filtering device which is able to utilize a single sheet of filter material which is quick and easy to handle in the laboratory and in the field that does not require expensive machining or molding operations during manufacturing of the filtering device and which will insure complete separation of the samples.
The present invention is directed primarily to a cell harvester and a method of filtering particularly useful for radioimmunoassays and biochemicals not only in the laboratory environment but also in the field. The demands of biochemistry have required a compact unit suitable for application at the situs of the testing for which the invention is portable, easy to use and of a compact and rugged construction. The filtering device unlike the prior art is relatively inexpensive to manufacture and easy to operate, resulting in effective and rapid separation of bound ligand receptor complexes from the free ligand for use in both the laboratory and in remote locations in the field. In addition, the device according to the present invention is able to use a single flat sheet of filter material to simultaneously collect the residue from a number of samples without risk of contaminating the individual samples.